Reproduction of sound



Dec. 19, 1933. J. sH W I HEPRQODUCTIONZVOF SOUND Filed July :50, i930 INV EN TOR. Jbsnw ASH/4W M4, A TTORNEYS.

Patented Dec. 19, 1933 7 1,939,726 REPRODUCTION OF SOUND Joseph Shaw,Hastings-ori-Hudson, N. Y., as-' signor to Paramount Publix Corporation,New

York, N. Y., a corporationof N ew -York Application July 30, 1930.Serial No. 471,642

10 Claims. (01. 179-1003) This invention is directed tosound'reproduction, and specifically to reproduction of soundphotographically recorded on a'film.

One of the objects of my invention is the-provision of a method andapparatus whereby superior results are obtained as compared with priormethods and means, my invention providing clearer and better definitionand greater intensity with a given power input.

10 A still further object of my invention is the provisionof a methodand apparatus for use in been recorded in theform of images of differentdegrees of densityfas distinguished from images of varying width.

In the reproduction of sound-so recorded it has been the custom toproject the rays from a light source of fixed intensity throughacondenser lens system, a light slit of fixed dimen sions and anobjective lens system upon thesound images on the film, the light rayswhich pass through the' film falling upon the window of'a photoelectrocell connected in an electric circuit. With such systems it has beenfound that pencil of light isfo'c'usedupon the film, and better resultswhen a very narrow slit aperture isplaced' between the optical'sy'stemand the lightsource, the focusing of a very narrow pencil jof light uponthe film reducing the 'overlapping of the frequency image lines on thefilm, thereby to' improve reproduction, I

" However, the narrow slit has its disadvantages filament lamp it isdifilcult for theaverage projectionistproperly to focus the light on thefilm,j

much trouble and poor reproduction resulting from the lamp being out ofalignment with the central axis of the light slit and from sagging of,the filament to throw the light image: line out of. focus. This lattercauses blurred reproduction and loss of high frequencies.

Another objection to the use of the very narrow light slit is the lightinterference which resultsfromyprojecting light through a narrow slit, aphenomena Well recognizedinphysicsnand 05 which'if great. care isnotexercised: in. properly best results are obtained when a verynarrowand drawbacks inasmuch as it involves loss of j light, andfurthermore when using the narrow slit and a lamp. with a coil filamentor a ribbon proportioning the slit also results in distortedreproduction.

I have found by a great number of trials that the drawbacks, some ofwhich have been enumerated above, can. be overcome by using one 03 ormore highly restricted circular apertures of" the nature of pinholes infront of the film, i. e., between the film and photoelectric cell. By.my method and apparatus the light source is focused on the-film, thelight rays after passing through 65.

the sound film passing through the minute aperture or apertures and fromthence to the photoelectric cell.

- I have found in practice that the sharper the photoelectric cellemission, the less amplification required, theemployment'of a highlyrestricted aperture i. e. a pin hole aperture between the film and cellI am able to obtain a better concentration of the light rays thanpossible with. the usual elongated aperture with a resultant in- 75.creasein the emission efiiciency. of the cell.

Consequently, comparing the results produced with the usual light slitemployed in reproduction with the results produced by meiwhen employingthe highly.restrictedfaperture or apertures of this invention, thevolume of reproduced sound is relatively increased.

I havediscovered also that the highly restrict-' ed aperture orapertures placed as inventedby me function as a lens'system to focus thesound v images upon the surface of the V photoelectric cell, the smallerthe aperture the better theresults obtained, theuseof my invention,therefore, improving the quality of reproduction.

The increased volume obtainedby me, therefore, I attribute to theincreased emission pressure upon the surface of the photoelectric cellcovered by the concentrated light rays passing through the highlyrestricted, minute aperture employed by meascompared to the effect ofthe light rayspassing through a slit as in present practice.

i The better sound definition obtained by the use of my invention Iattribute to the use of a minute aperture intermediate the film and celland so placed with respect to the film that only the light rays passingthrough a single frequency image at a time are projected uponthe cell,therebyavoiding the frequency overlapping, asmet with in presentpractice. I

Itwill be appreciated also that inasmuch as the aperture is in front ofthe film,- i. e., between, the film and, the lightsensitive electricdeviceorcell, the, projectionistis not called upon constant- 1y to watchthe filament of the light source to see as the light rays under myinvention are not focused upon a restricted light slit before strikingthe film, as under present practice, but are projected directly upon thefilm, so that even with reasonable sagging of the filament the lightrays will still strike the film and cover the minute aperture in frontof the film.

I prefer, however, as an aid to the operator in centering the light raysupon the film to employ a slit back of the film, i. e., between thelight source and film. This slit, however, is relatively wide, six mils,for example, as compared with the one mil aperture or slit now used.

In the drawing:

Fig. 1 illustrates diagrammatically one embodiment of my invention;

Fig. 2 is a modification;

Fig. 3 is a further modification; and

Fig. 4 a still further modified embodiment of my invention.

Referring first of all to the embodiment of my invention illustrated inFig. 1: 1 designates a light source of constant intensity. This lightsource may be of the same type as those now employed using either a coilor a ribbon filament. 2 designates a lens system embodying as iscustomary a condensing lens system 3, and objective lens system 4intermediate the light source and film. 5 is the film on which the soundto be reproduced has been photographed, the frequency images on thisfilm being of varying degrees of intensity, varying with the originalsound recorded.

6 illustrates diagrammatically a photoelectric cell or light sensitiveelectric device which it will be understood is connected electrically inthe usual way to an amplifier and loud speaker, not shown. The cell,amplifier and loud speaker may be of usual construction.

Prior to my invention, in an installation of this character, a one millight slit would be employed intermediate the condensing lens system 3and the objective lens system 4, the light rays from the light source 1being focused by the projectionist upon this slit so that the image ofthe slit is focused upon the film, the light rays then passing throughthe slit and through the film and falling upon the surface or window ofthe photoelectric cell 6. By the present invention, however, I haveeliminated the necessity for the narrow slit just mentioned with itsinherent drawbacks above referred to and provide a highly restricted,minute circular aperture. in front of the film 5 intermediate it and thephotoelectric cell 6. The aperture plate in which the aperture orapertures are provided is designated'l, and as will be seen from thedrawings is located in close proximity to the film.

I have found by a great many tests that no particular skill is requiredon the part of the projectionist to direct the lightrays from the lightsource 1 upon the film 5 in such a manner that the light rays will passthrough this film and through the pinhole aperture '7 to thephotoelectric cell 6. I find also that any sagging of the filamentof thelight source met with in practice is not detrimental, the light raysdespite such sagging striking the film 5 to pass therethrough and fromthence through the aperture or apertures 7'.

I have found also that by the use of the aperture or apertures 7' I amenabled to obtain a better concentration of the light rays upon theaperture 7 to the cell, so that an increase is obtained in the cellemission as compared with present practice. 7

whether or not the same has sagged, inasmuch I have found also thatinasmuch as the aperture 7' is so highly restricted as to be extremelyminute overlapping of frequency images projected upon the photoelectriccell is avoided with the result that reproduction is ideally clear.

As above mentioned I have found also that comparing my system with priorsystems, taking a given power input, there is a marked relative increasein output with my system. This is apparently due to the increasedpressure on the photoelectric cell produced by the concentrated lightrays passing through the highly restricted aperture 7' placed in frontof the film as distinguished from the use of a one mil slit behind thefilm.

In Fig. 2 I have shown a slightly modified embodiment of my invention inthat I have provided a mechanical slit 8 intermediate the two lenssystems 3 and 4. This slit or aperture 8 is employed merely as aconvenient means of facilitating directing of the light rays from thelight source 1 upon the film 5 in line with the pinhole aperture '7'. Inother words, it will make the work of the projectionist easier incentering his light.

In Fig. 3 I have employed the apparatus of Fig. 2, and in addition Ihave provided a lens system 9 between the aperture '7' and thephotoelectric cell. This lens system 9 enables me to project a sharperimage on the face of the photoelectric cell 6 than where this lenssystem is omitted.

In Fig. 4 the apparatus employed is similar to that of Fig. 3 exceptthat in this instance I have protected the aperture '7 against dust orother foreign materials by enclosing the same in the tube of the lenssystem 9, the aperture being located in this tube intermediate the twolenses of this system which-have been designated 10 and 11,respectively.

It will be appreciated from all of the foregoing that my inventionprovides for the interposition of a very highly restricted apertureintermediate the sound film and light sensitive electrical device, theaperture being so located with respect to the film that light rayspassing through the film and aperture are concentrated upon the surfaceof the electrical device, thereby insuring desired intensity ofreproduction without increase in power input.

It will be appreciated also that the nature and location of the apertureemployed are such that overlapping of frequency images upon the lightsensitive electric device is avoided.

, It will be seen also that inasmuch as the aperture or apertures 7employed by me are so highly restricted in area, such apertures lendthemselves for use in connection with sound records much less in widththan standard records, .thereby adapting my invention for use inconnection with sound motion picture projectors for home use, where theapparatus is necessarily simplified as compared with the apparatus usedby professionals, and wherein a reduction in the width of the soundtrack would be of great advantage.

What I claim is:-

1. In an apparatus for reproducing sound from a variable density soundfilm, the combination of a light source behind the film, a photoelectriccell in front of the film, and an aperture plate having a pinholeaperture intermediate the cell and film. I

2. In an apparatus for reproducing sound from a variable density soundfilm, the combination of a light source behind the film, a photoelectriccell LOO in front of the film, an aperture plate having a pinholeaperture in front of the film intermediate the cell and film, and acondensing and objective lens system behind the film intermediate thefilm and light source.

3. In an apparatus for reproducing sound from a variable density soundfilm, the combination of a light source behind the film, a condensinglens and an objective lens and an intermediate light slit behind thefilm intermediate the film and light source, a photoelectric cell infront of the film, and an aperture plate having a pinhole apertureintermediate the cell and film.

4. In an apparatus for reproducing sound from a variable density soundfilm, the combination of a light source behind the film, a photoelectriccell in front of the film, an aperture plate having a pinhole aperturein front of and adjacent to the film and intermediate the cell and film,and an objective lens system intermediate the aperture plate and cell.

5. In an appaartus for reproducing sound from a variable density soundfilm, the combination of a light source behind the film, a photoelectriccell in front of the film, a lens tube intermediate the film and cell,lenses in said tube, and an aperture plate having a pinhole aperturelocated in said tube intermediate said lenses.

6. In an apparatus for reproducing sound the combination of a sound filmcarrying variable density sound images, a light source of fixedintensity behind the film, a photoelectric cell in front of the film,and an aperture plate intermediate the said cell and film and in thepath of the light rays passing through said film from said light source,said plate being provided with a pinhole aperture so restricting thelight rays passing from the light source through the film to saidphotoelectric cell that the projection of overlapping sound images onthe photoelectric cell is avoided.

7. In an apparatus for reproducing sound, the combination of a soundfilm carrying variable density sound images, a light source of fixedintensity behind the film, a condensing and objective lens systemintermediate said film and light source, a photoelectric cell infront ofthe film, an aperture plate intermediate the said cell and film and inthe path of the light rays passing through said film from said lightsource, said plate being provided with a pinhole aperture restrictingthe light rays passing to the photoelectric cell at any instant to asingle sound image.

8. In an apparatus for reproducing sound, the combination of a soundfilm carrying variable density sound images, a light source of fixedintensity behind the film, a condensing lens and an objective lens andan intermediate light slit behind the film intermediate it and the lightsource, a photoelectric cell in front of the film, and an aperture plateintermediate the said cell and film and in the path of the light rayspassing through said film from said light source, said plate beingprovided with a pinhole aperture so to restrict the light rays passingfrom the light source through said film to the photoelectric cell thatthe projection of overlapping sound images on the photoelectric cell isprevented.

9. In an apparatus for reproducing sound, the combination of a soundfilm carrying variable density sound images, a light source of fixedintensity behind the film, a photoelectric cell in front of the film, anaperture plate intermediate the said slit and film and in the path ofthe light rays passing through said film from said light source, saidplate being provided with a pinhole aperture so restricting the lightrays passing from the light source through the film to saidphotoelectric cell that the projection of overlapping sound images onthe photoelectric cell is avoided, and an'objective lens systemintermediate said aperture plate and cell.

10. In an apparatus for reproducing sound, the combination of a soundfilm carrying variable density sound images, a light source of fixedintensity behind the film, a photoelectric cell in front of the film, alens tube intermediate the film and cell, lenses in said tube, and anaperture plate located in said tube intermediate said lenses andintermediate the said cell and film and in the path of the light rayspassing through said film from said light source, said plate beingprovided with a pinhole aperture restricting the light rays passing tothe photoelectric cell at any instant to a single sound image.

JOSEPH SHAW.

CERTIFICATE OF CORRECTION.

Patent No. 1,939,726. December 19, 1933,

JOSEPH SHAW.

It is hereby certified that error appears in the printed specificationof the above numbered patent requiring correction as follows: Page 2,beginning with line 142, strike out all to and including line 28, page3, comprising claims 1 to 5 inclusive; and the claims appearing in thepatent as numbers 5 'Z, 8, 9, and 10, should bear the numbers i, 2, 3,4, and 5 respectively; and that the said Letters Patent should be readwith these corrections therein that the same may conform to the recordof the case in the Patent Office.

Signed and sealed this 30th day of January, A. D. 1934.

F. M. Hopkins (Seal) Acting Commissiener oi Patents

